what is the difference between Image element and Drawing element? What is the Image element for? what can you do with it?

Image elements are for Raster files (bitmap drawings).
You cannot edit these directly inside TBS but must use
Paint, Photoshop, GIMP or some other bitmap editing software to create them.

Drawing elements are vector elements, these are what you
create and draw in when you are using Toon Boom Studio drawing and painting tools.